This invention relates to sensing or detecting and measuring odors and in particular is aimed at detecting and measuring odors in the field, i.e., not under laboratory conditions.
U.S. Pat. No. 6,018,984 and an earlier U.S. Pat. No. 3,902,851, referenced in the ""984 patent, discuss and describe in considerable detail olfactometers for detecting and measuring air polluting odors. These devices are quite sophisticated and are used as laboratory instruments in which the sample odors are fed from a container into the olfactometer in various dilution ratios commonly known as D/T, (xe2x80x9cDilution to Thresholdxe2x80x9d). In the device described in the ""984 patent odorous air is fed to a venturi mixing nozzle through various branches containing solenoid operated valves and different sized orifices for mixing with odor-free air to provide various D/T levels. The prior art also includes a device for field use for detecting and measuring air pollution in the form of a Scentometer manufactured and sold by Barnebey and Sutcliffe Corporation (now Barnebey-Cheney Company). The Scentometer essentially is a rectangular clear plastic box containing two chambers of activated carbon, two nasal outlet ports for sniffing separately into each nostril, two air inlets (one for each activated carbon bed) and six odorous air inlets of different sizes, to provide the various D/T ratios, which are directly connected with a mixing chamber and the nasal outlets. Odorless or odor-free air is obtained by air being drawn through beds of carbon and filtered air is mixed with the odorous air. The Scentometer user follows the generally accepted or standard practice of detecting and measuring the odor by first sniffing with the smallest odorous air inlet opening (lowest D/T ratio) and then successively opening the next largest odorous air inlet until the user or tester finds that an odor is discernible. The size of the opening or orifice for the odor inlet at which the odor is discernible then indicates to the tester the approximate concentration of the odor or the odor level. In the past, conventionally D/T was calculated by dividing the volume of odor free air by the volume of odorous air but more recently, the more sophisticated laboratory instruments calculate D/T by dividing the total air flow volume by the volume of odorous air.
The present invention utilizes a fairly small lightweight housing suitable to be hand carried so it is convenient to use in the field. The housing contains a hollow tube or barrel open at both ends. One end is the air input end, the other is the air output end. Odorous air, i.e., the ambient polluted air, enters the inlet end and travels down the tube to the outlet end to which is attached a nose mask for directing the air to the sensor or tester""s nostrils when the user inhales. The nose mask also has an outlet opening and there are check valves for the nose mask inlet openings and outlet openings so that the former is open and the latter closed when the user inhales and vice versa. Odorless or odor-free air is obtained from ambient air passing through a multi-media filter and is fed into the housing where it is mixed with the polluted or odorous air at the inlet end of the barrel. In the preferred form a disk having a series of apertures is rotatably attached to the housing at the air inlet end of the barrel with the apertures containing inserts having respectively different sized orifices and thicknesses. The disk is rotated by the user to bring each aperture successively to a position opposite the inlet opening of the barrel and sniffs as necessary to draw the air mixture into the nose mask. The setting at which the odor is discernible gives the D/T ratio. Filtering the ambient air through a multi-media filter instead of through a carbon filter as in the Scentometer provides a more universal and more complete filtering of odors out of the ambient air that is used to mix with the odorous air. Preferably these filters are commercially available devices which can be releasably secured to the housing in some convenient fashion such as snapping or press-fitting or threading them into place. They are suitably sealed to prevent any leakage of any of the polluted air into the odor-free air passageway yet they are attached in some fashion so they can be easily and quickly removed and replaced as necessary.